1) 5x+y=20
5x+y-20=0
2) x-2y=-7
x-2y+7=0
5x+y=20,
x-2y=-7; ×(-5)
-5x+10y=35;
11y=55,
5x+y=20;
y=5
y=5,
5x=15;
x=3.
1) 5x+y=20
5x+y-20=0
2) x-2y=-7
x-2y+7=0
5x+y=20,
x-2y=-7; ×(-5)
5x+y=20,
-5x+10y=35;
11y=55,
5x+y=20;
y=5
5x+y=20;
y=5,
5x=15;
y=5,
x=3.